Adaptive capacity of Barbary ewes to underfeeding and re-feeding periods: effects on adipose tissues.

Thirty Barbary ewes were divided into three groups according to body weight (48.7 kg) and body condition score. The first group (TT) was fed its requirements (100 % of theoretical energy requirements), and two other groups were severely underfed (20 % of energy requirements). By the end of the underfeeding period, the ewes of one group (B) were slaughtered, while the ewes of the remaining group (BH) were re-fed until they reached their initial body weight. These ewes were then slaughtered, together with those of the TT group. The body tissues were dissected and divided into fat, muscle and bone. Diets were made of vetch-oat hay, added with barley grain during the refeeding periods. The duration of the survival period of these Barbary ewes was 161 days and the re-feeding period tasted 154 days, so that the complete cycle was achieved within 315 days. The ewes fed at maintenance (TT) had a constant body weight during the whole experiment, whereas the underfed ewes (B) lost 17.5 kg. By the end of the recovery period, the BH ewes gained 20.1 kg of their body weight and reached 51.5 kg. At almost the same body weight, the re-fed ewes (BH) had a higher (+1.6 kg) total fat content (11.9 kg) than those maintained at a constant body weight (10.3 kg). The TT and BH ewes had almost four times more adipose tissue than the ewes (B) that were under-fed (3.3 kg). The adipose tissue variations (-8.8 kg) were more important than changes in muscular mass (-3.4 kg). Far adipose tissue of the tail varied between 2.7 kg in the well-fed ewes and 0.6 kg in the underfed ewes. In these fat-tailed ewes, the order of adipose tissue mobilization, estimated by allometry coefficients, was in general agreement with observations made in thin-tailed ewes. Furthermore, the ability of fat tissue from the tail to be mobilized was closer to the internal fat rather than the subcutaneous fat. Hence, it can be considered that the fat from the tail of Barbary ewes exerts its role of body reserves more by its mass than by its ability to be rapidly mobilized. This experiment shows clearly the ability of Barbary sheep to survive in situations of food shortage of long duration. ((C) Elsevier / Inra).